mailman doesn't exist?

a customer complained he was not getting to send mail to his mail list created on cPanel
I tried and got this on exim_mainlog:
2005-10-10 16:13:46 1EP35m-0006Bv-Do ** x@x R=mailman_virtual_router T=mailman_virtual_transport: Child process of mailman_virtual_transport transport returned 127 (could mean unable to exec or command does not exist) from command: /usr/local/cpanel/3rdparty/mailman/mail/mailman